A report by an environmental group says that only 20 per cent of surveyed restaurants in Beijing have been observing an indoor smoking ban that became law in May.

The Daerwen Nature Quest Agency, a civil environmental group, surveyed 51 restaurants in the capital between May and September and found that only 10 observed a complete ban, while 16 restaurants had a partial ban. The remainder had not banned smoking.

The restaurants serve working- and middle-class patrons.

The report also found that in restaurants where smoking continued, tests had shown that the air had almost twice the amount of hazardous particles compared with restaurants that complied with the ban.

Daerwen Nature Quest said that after 16 years of toying with anti-smoking measures in Beijing, it was time for the capital to impose a complete indoor smoking ban.

Beijing first introduced a smoking ban in public places in 1995, and another one in 2008 as part of its Olympic pledges. However, smoking areas were allowed, which led to the problem of second-hand smoke.

According to data from the China Centre for Disease Control and Prevention, about 740 million people on the mainland are affected by second-hand smoke, with restaurants accounting for 88 per cent of such exposure.

Another report last year from the International Union against Tuberculosis and Lung Disease said more than 100,000 people die every year from exposure to second-hand smoke on the mainland.

However, progress on tobacco control has been slow, despite the government's ratification six years ago of a World Health Organisation tobacco-control agreement, which obliged China to impose smoking bans in all indoor public places, work places and public transport by January 9 this year.

The Ministry of Health amended a regulation that bans smoking in all indoor public places from May, but the lack of stiff penalties and promotion of the ban are two reasons why the ban was not properly enforced.

Another problem is that the State Tobacco Monopoly Administration, which handles tobacco policy and regulation, also administers China National Tobacco, the biggest tobacco maker in the world, analysts said.